Expression of CXCL6 and BBS5 that may be glaucoma relevant genes is regulated by PITX2

The transcription factor PITX2 is implicated in glaucoma pathology. In an earlier study we had used microarray analysis to identify genes in the trabecular meshwork (TM) that are affected by knock down of PITX2. Here, those studies were pursued to identify genes that are direct targets of PITX2 and that may be relevant to glaucoma. Initially, bioinformatics tools were used to select among the genes that had been affected by PITX2 knock down those that have PITX2 binding sites and that may be involved in glaucoma related functions. Subsequently, the effect of PITX2 was tested using the dual luciferase assay in four cell cultures including two primary TM cultures co-transfected with vectors containing promoter fragments of six candidate genes upstream of a luciferase gene and a vector that expressed PITX2. Finally, the effect of PITX2 on endogenous expression of two genes was assessed by over expression and knock down of PITX2 in TM cells. Thirty four genes were found to contain PITX2 binding sites in their putative promoter regions, and 16 were found to be associated with TM-specific and/or glaucoma associated functions. Results of dual luciferase assays confirmed that two of six genes tested were directly targeted by PITX2. The two genes were CXCL6 (chemokine (C-X-C motif) ligand 6) and BBS5 (Bardet-Biedl syndrome 5). Over expression and knock down of PITX2 showed that this transcription factor affects endogenous expression of these two genes in TM cells. CXCL6 encodes a pro-inflammatory cytokine, and many studies have suggested that cytokines and other immune system functions are involved in glaucoma pathogenesis. BBS5 is a member of the BBS family of genes that affect ciliary functions, and ciliary bodies in the anterior chamber of the eye produce the aqueous fluid that affects intraocular pressure. Immune related functions and intraocular pressure are both important components of glaucoma pathology. The role of PITX2 in glaucoma may be mediated partly by regulating the expression of CXCL6 and BBS5 and thus affecting immune functions and intraocular pressure.

The chemokine receptor CXCR6 controls the functional topography of interleukin-22 producing intestinal innate lymphoid cells

Interleukin-22 (IL-22) plays a critical role in mucosal defense, although the molecular mechanisms that ensure IL-22 tissue distribution remain poorly understood. We show that the CXCL16-CXCR6 chemokine-chemokine receptor axis regulated group 3 innate lymphoid cell (ILC3) diversity and function. CXCL16 was constitutively expressed by CX3CR1(+) intestinal dendritic cells (DCs) and coexpressed with IL-23 after Citrobacter rodentium infection. Intestinal ILC3s expressed CXCR6 and its ablation generated a selective loss of the NKp46(+) ILC3 subset, a depletion of intestinal IL-22, and the inability to control C. rodentium infection. CD4(+) ILC3s were unaffected by CXCR6 deficiency and remained clustered within lymphoid follicles. In contrast, the lamina propria of Cxcr6(-/-) mice was devoid of ILC3s. The loss of ILC3-dependent IL-22 epithelial stimulation reduced antimicrobial peptide expression that explained the sensitivity of Cxcr6(-/-) mice to C. rodentium. Our results delineate a critical CXCL16-CXCR6 crosstalk that coordinates the intestinal topography of IL-22 secretion required for mucosal defense.

Gene expression profiling of connective tissue growth factor (CTGF) stimulated primary human tenon fibroblasts reveals an inflammatory and wound healing response in vitro

PURPOSE

The biologic relevance of human connective tissue growth factor (hCTGF) for primary human tenon fibroblasts (HTFs) was investigated by RNA expression profiling using affymetrix(TM) oligonucleotide array technology to identify genes that are regulated by hCTGF.

METHODS

Recombinant hCTGF was expressed in HEK293T cells and purified by affinity and gel chromatography. Specificity and biologic activity of hCTGF was confirmed by biosensor interaction analysis and proliferation assays. For RNA expression profiling HTFs were stimulated with hCTGF for 48h and analyzed using affymetrix(TM) oligonucleotide array technology. Results were validated by real time RT-PCR.

RESULTS

hCTGF induces various groups of genes responsible for a wound healing and inflammatory response in HTFs. A new subset of CTGF inducible inflammatory genes was discovered (e.g., chemokine [C-X-C motif] ligand 1 [CXCL1], chemokine [C-X-C motif] ligand 6 [CXCL6], interleukin 6 [IL6], and interleukin 8 [IL8]). We also identified genes that can transmit the known biologic functions initiated by CTGF such as proliferation and extracellular matrix remodelling. Of special interest is a group of genes, e.g., osteoglycin (OGN) and osteomodulin (OMD), which are known to play a key role in osteoblast biology.

CONCLUSIONS

This study specifies the important role of hCTGF for primary tenon fibroblast function. The RNA expression profile yields new insights into the relevance of hCTGF in influencing biologic processes like wound healing, inflammation, proliferation, and extracellular matrix remodelling in vitro via transcriptional regulation of specific genes. The results suggest that CTGF potentially acts as a modulating factor in inflammatory and wound healing response in fibroblasts of the human eye.

Overexpression of CXCL16 promotes a vulnerable plaque phenotype in Apolipoprotein E-Knockout Mice

BACKGROUND

CXCL16 has been shown to be involved in atherosclerotic lesion development, but its role in preexisting lesions is still unclear. This study aims to assess the effect of CXCL16 on the stability of preexisting lesions.

METHODS

We firstly measured plasma CXCL16 level in Apolipoprotein E-Knockout (ApoE KO) mice with either high-cholesterol diet (HCD) or normal diet (ND) by enzyme-linked immunosorbent assay (ELISA). Then, silastic collars were placed around the carotid arteries in HCD-ApoE KO mice to accelerate atherosclerotic lesions. Five weeks later, CXCL16 was overexpressed by intravenous injection of lentivirus carrying CXCL16 transgene. Two weeks after infection, lesions were stained with hematoxylin and eosin (HE) and with oil red O. Biomarkers in the lesions, such as MMPs, CCL2, VCAM-1 and TNF-α were measured by real-time polymerase chain reaction (RT-PCR), which indicate the instability of plaques.

RESULTS

The level of CXCL16 in plasma was higher in HCD-ApoE KO mice as compared to ND-ApoE KO mice. Circulating CXCL16 overexpression does not affect the size of preexisting plaques, but it leads to vulnerable plaque morphology and increases the expression of markers of plaque destabilization.

CONCLUSION

Systemic CXCL16 becomes much higher in atherosclerosis, and it could be a potential atherogenic biomarker. Overexpression of CXCL16 promotes the evolution of preexisting lesions to vulnerable plaques in ApoE KO mice.